Conventionally, induction cooking devices of this type have been adapted to determine the capacitances of electrodes placed on the lower surface of a top plate and determine the occurrence of boiling over on detecting increases of these capacitances and then stop heating operations or decrease the high-frequency electric current flowing through a heating coil (refer to Unexamined Japanese Patent Publication No. 2008-159494 (Patent Literature 1), for example). In this structure, the phenomenon that, if liquid is boiled over to spread on the top plate upper surface around the electrodes, the capacitances of the electrodes increase to be larger than those of when no boiling over has occurred is used.
FIG. 3 is a view illustrating the structure for detecting boiling over, in the conventional induction cooking device described in Patent Literature 1.
As illustrated in FIG. 3, the conventional induction cooking device includes a driving circuit 102 to supply high-frequency electric power to a heating coil 104 when low-frequency electric power is inputted thereto from an AC power supply 101, in order to inductively heat a container to be heated (not illustrated). Further, a plurality of circular electrodes 103 are dispersively placed near the outer periphery of the heating coil 104. The respective circular electrodes 103 placed dispersively are connected to a capacitance determination circuit 106. The capacitance determination circuit 106 detects the capacitance between each circular electrode 103 and the capacitance determination circuit 106. A control circuit 105 is adapted such that signals from the capacitance determination circuit 106 are inputted thereto and is adapted to determine the temperature of the container being heated control heating operations of the driving circuit 102 based on boiling-over detection operations and the results of the detection. The capacitance determination circuit 106 detects boiling over on detecting abrupt increases in the capacitances of the circular electrodes 103 and stops detecting boiling over until the container being heated reaches a predetermined temperature which induces boiling over.    PLT 1: Unexamined Japanese Patent Publication No. 2008-159494